k-Wave Toolbox

expandMatrix

Enlarge a matrix by extending the edge values

Syntax

mat_new = expandMatrix(mat, exp_coeff)
mat_new = expandMatrix(mat, exp_coeff, edge_val)

Description

expandMatrix enlarges an input matrix by extension of the values at the outer faces of the matrix (endpoints in 1D, outer edges in 2D, outer surfaces in 3D). Alternatively, if an input for edge_val is given, all expanded matrix elements will have this value. The values for exp_coeff are forced to be real positive integers (or zero). Note, indexing is done inline with other k-Wave functions using mat(x) in 1D, mat(x, y) in 2D, and mat(x, y, z) in 3D.

For example, running

mat = magic(3);
expandMatrix(mat, 1)
expandMatrix(mat, [2 0 1 0], 0)

will give the outputs

ans =

     8     8     1     6     6
     8     8     1     6     6
     3     3     5     7     7
     4     4     9     2     2
     4     4     9     2     2

ans =

     0     0     0     0     0
     0     0     8     1     6
     0     0     3     5     7
     0     0     4     9     2

Inputs

mat

the matrix to enlarge

exp_coeff

the number of elements to add in each dimension, where

exp_coeff = [a] or [x_start, x_end] in 1D

exp_coeff = [a] or [x, y] or [x_start, x_end, y_start, y_end] in 2D

exp_coeff = [a] or [x, y, z] or [x_start, x_end, y_start, y_end, z_start, z_end] in 3D

(here a is applied to all dimensions)

Optional Inputs

edge_val

value to use in the matrix expansion

Outputs

mat_new